Can you please share the full config files and the log files if possible? Which other beats are you running? What is your setup? beats -> LS -> ES? Is the memory constantly increasing or do you see it going up and down?

please share full output section in filebeat.yml and other settings, but prospectors. The publish_async option looks telling. But as publish_async changes interaction with output I need to know about outputs in order to figure there might be some issue. You using multiline? Have you checked filebeat logs for output errors (e.g. EOF or connections being dropped)?

In prospectors have you a common strategy using any of the close_... settings?

Have you tried to disable publish_async?

Filebeat supports generation of a memory profile using -memprofile <out file name>. Can you run filebeat with this setting and share the generated profile with us?